Total Effluent Volume Research Articles

Comparing the effectiveness of full-vacuum and half-vacuum drainage in reducing seroma after modified radical mastectomy: a meta-analysis.

Owing to limited outpatient support for drain management, delayed discharge after mastectomy is more prevalent in developing countries. Utilising half-vacuum (HV) suction drains for routine drainage after mastectomy could lead to a reduced incidence of seroma and a shorter hospital stay. This systematic review and meta-analysis compared the outcomes of HV against full-vacuum (FV) suction drains in patients who underwent modified radical mastectomy for breast cancer. Differences between the two groups in length of hospital stay, total volume of drain effluent and incidence of seroma were assessed. RevMan 5.4 was used to calculate the odds ratio (OR) and relative risk (RR) for dichotomous data, and the mean difference (MD) for continuous data. Nine randomised controlled trials were included in this review. Using HV drains reduced both the mean length of hospital stay (MD: -2.30 days, 95% confidence interval [CI]: -4.10 to -0.49 days, I2=97%) and the mean total volume of effluent (MD: -132.61ml, 95% CI: -207.32ml to -57.91ml, I2=88%) compared with FV drains. However, there was no statistically significant difference in incidence of seroma between the two groups (RR: 0.67, 95% CI: 0.30 to 1.46, I2=65%). Likewise, there was no difference in rate of seroma occurrence on sensitivity analysis (OR: 1.29, 95% CI: 0.72 to 2.33, I2=74%). There was no difference in the incidence of seroma between HV and FV suction drainage. Conversely, a reduction in the length of hospital stay and the total volume of drain effluent was observed for mastectomy patients with a HV drain.

Nierenersatztherapie

The clinical indications for initiating acute renal replacement therapy (ARRT) include life-threatening refractory disturbances of electrolyte, acid-base and fluid balances as well as severe clinical symptoms of the uremic syndrome. In most other cases a watch and wait strategy is justified; however, a consistent (at least daily) re-evaluation is mandatory. In intensive care patients with persistent oliguria or anuria for > 72 h despite stable hemodynamics and adequate volume status, initiation of RRT should be considered even in the absence of urgent clinical indications. For continuous RRT the guidelines recommend a total effluent volume (dialysate plus filtrate) of 20–25 ml/kg body weight/h which usually requires a higher prescription of effluent volume. The treatment duration and frequency of intermittent RRT should primarily be tailored to the patients’ individual needs regarding fluid, electrolyte, and acid-base balances. Treatment sessions every 2 days will usually be sufficient to achieve adequate solute clearance. Basic prerequisites for attempts at weaning from ARRT are stable hemodynamics, adequate fluid, electrolyte, and acid-base statuses and a urine output of at least 500 ml/24 h or a positive response to a furosemide stress test. The successful recovery of kidney solute clearance can be demonstrated by performing an endogenous creatinine clearance or quantification of the kinetic estimated glomerular filtration rate (KeGFR).

Kidney Replacement Therapy for Patients Requiring Cardiopulmonary Bypass Support during Cardiac Surgery.

Kidney Replacement Therapy for Patients Requiring Cardiopulmonary Bypass Support during Cardiac Surgery.

On relaxation of the influences of treated sewage effluent on an adjacent seaweed farm in a tidal strait

An Eulerian passive tracer model coupled with a quadruple-nested 3D circulation model was used to assess the coastal dispersal of treated wastewater effluent from a sewage treatment plant and the associated impacts on an adjacent seaweed farm using three different operational scenarios. When the discharged volume and source effluent fluxes were decreased by ~16.7%, the accumulated effluent in the farm was reduced by ~25.4%. A tracer flux budget analysis revealed the apparent predominance of the transient component that accounts for the nonlinear interactions primarily from tidal currents and eddies. The transient flux promoted the effluent influx to impede effluent accumulation in the farm, whereas the mean flux contributed to the outgoing flux. A source flux reduction caused a remarkable decrease in the transient flux and thus an even greater effluent accumulation reduction. In turn, a modified source density scenario without total effluent volume change did not work as expected.

The Clear Space Index.

Kt/V for urea (Kt/V) is a dimensionless clinical index of dialysis dose; however, it does not directly reflect the removal capacity of the solute. Since the total amount of solute removal, M, is directly proportional to the initial solute concentration CB(0), it is reasonable to introduce an index by dividing M by CB(0). This index was termed 'clear space' (CS) because it was later found that it reflects the body fluid volume, the concentration of which becomes zero by the treatment. Although CS originally requires measurement of M, storing all the effluent of dialysis fluid, it may be more easily calculated by measuring concentrations in blood, using a simpler formula without storing any effluent of dialysis fluid. Moreover, this technique is applied not only for urea, but also for much larger solutes. The concept of CS is also applied to peritoneal dialysis, identifying the maximum CS relative to the total effluent volume of the dialysis fluid. It was shown by CS analysis that the 1-compartment model may not work well, even for small solutes like urea, under higher levels of solute removal. It was also shown that divergence from the 1-compartment model was greater in patients with regenerated cellulose membranes than in those with synthetic polymeric membranes. Key Messages:CS is a simple yet useful solute removal index that avoids the effect of CB(0) and may be used for comparison of dose among two or more treatment modalities. Unlike Kt/V, CS can be measured for all kinds of solute, giving the average for two or more compartments in which the concentration of solute of interest becomes zero.

A Runoff and Sediment Routing Model for Open Lot Beef Feeding Facilities

Abstract. Feedlot runoff is a potential environmental contaminant and requires proper management to minimize impact on water quality. In designing runoff management systems, accurately assessing the amount of runoff that will be generated is of foremost importance. Along with overall quantity of runoff, the temporal pattern, both throughout the year and within an individual storm event, can have important implications for sizing control system components, in determining the performance the control system achieves, and in the overall pollution potential of the feedlot. This review summarizes the hydraulic properties of the feedlot surface, specifically focusing on variables that impact the total volume of effluent generated and the resulting amount of sediment transported. The work cumulates in development of a feedlot runoff routing model, presented as a series of equations that are implemented within the updated Iowa State University-Vegetative Treatment Area model, with a sediment transport/erosion component. Overall, the results indicated that a curve number of 91 was best for estimating runoff volumes, but substantial variation about this value could occur. The calibrated model was able to accurately estimate average total solids concentrations of lots of different size, shape, and surface condition under different hydraulic situations (R 2 = 0.92 for calibration and the slope of the measured vs. modeled data was not different than one during model validation). Most calibration and validation feedlots were earthen, had the majority of runoff from rainfall events, had mounds within the pen, and were scraped only once or twice per production cycle; thus model performance may be limited for other situations. The feedlot runoff and sediment routing components were used to assess the impact of various feedlot design characteristics, including feedlot area, aspect ratio, and slope, on solids transport from the feedlot surface. This model can be used to evaluate the risk that feedlot runoff poses to water quality for prioritizing feedlots that are in need of enhanced runoff control systems, and to evaluate the hydraulic and sediment loadings that a runoff control system is required to handle.

Solute clearance in CRRT: prescribed dose versus actual delivered dose

Substantial efforts have been made toward defining the dose threshold of continuous renal replacement therapy (CRRT) associated with improved survival in critically ill patients with acute kidney injury. Published studies have used prescribed effluent rates, expressed as total effluent volume (TEV) per weight and unit time (mL/kg/h), as a surrogate for dose. The purpose of this study was to compare differences in CRRT dose based on prescribed effluent rate, measured TEV and direct measurement of urea and creatinine clearance. We analyzed data that had been prospectively collected on 200 patients enrolled in a randomized trial comparing survival with a prescribed effluent rate of 20 mL/kg/h (standard dose) to 35 mL/kg/h (high dose) using pre-dilution continuous venovenous hemodiafiltration (CVVHDF). Filters were changed every 72 h. Blood urea nitrogen (BUN), serum creatinine (SCr), effluent urea nitrogen (EUN) and effluent creatinine (ECr) were collected daily. Actual delivered dose was calculated as: (EUN/BUN)*TEV for urea and (ECr/SCr)*TEV for creatinine. Data were available for 165 patients. In both groups, prescribed dose differed significantly from the measured TEV dose (P < 0.001). In the standard dose group, there was no difference between the measured TEV dose and actual delivered urea and creatinine clearances. However, in the high-dose group, measured TEV dose differed significantly from delivered urea clearance by 7.1% (P < 0.001) and creatinine clearance by 13.9% (P < 0.001). Dose based on prescribed effluent rate or measured TEV is a poor substitute for actual CVVHDF creatinine and urea clearance.

Compared performance of a conceptual and a mechanistic hydrologic models of a green roof

AbstractIn order to investigate the hydrologic response of a green roof system within the urban environment, a monitoring campaign is carried out at the green roof site of the University of Genova (Italy). Experimental data confirm that the green roof is able to significantly mitigate the generation of runoff with median values of retained volume and peak reduction, respectively, equal to 94 and 98%. A conceptual linear reservoir and a simple mechanistic (Hydrus‐1D) models are implemented to simulate the hydrologic behaviour of the system; each model is calibrated and validated based on experimental data collected at the green roof site. The hydrographs simulated with both hydrologic models reproduce with acceptable matching capabilities the experimental measurements, as confirmed by the Nash‐Sutcliffe Efficiency index generally greater than 0·60. Although the relative percentage differences evaluated for the selected hydrograph variables (the total effluent volume, the peak flow rate and the hydrograph centroid) demonstrate that the mechanistic model is more accurate, prediction errors of the conceptual model are generally limited when compared with the observed hydrologic performance. Results of the present comparison are useful in supporting conceptual model selection in case the hydrologic response is addressed for hydrologic performance assessment. Copyright © 2011 John Wiley &amp; Sons, Ltd.

177 Solute Clearance in CRRT: Comparing Measured Effluent Volume to Actual Delivered Dose

SOLUTE CLEARANCE IN CRRT: COMPARING MEASURED EFFLUENT VOLUME TO ACTUAL DELIVERED DOSE William Lyndon, Keith Wille, Ashita Tolwani University of Alabama at Birmingham, Birmingham, AL, U.S.A. Substantial efforts have been made towards defining the dose threshold of continuous renal replacement therapy (CRRT) associated with improved survival in critically ill patients with acute kidney injury. Published studies have based dose of CRRT on small solute clearance, expressed as total effluent volume (TEV) per weight and unit time (ml/kg/hr). These studies have not compared CRRT dose based on the measured TEV to the actual delivered dose as determined by direct quantitative measurement of the solute in the effluent. The purpose of this study was to determine whether the measured TEV corrected for pre-dilution replacement fluid (RF) accurately estimates actual delivered small solute clearance. We retrospectively analyzed data that had been prospectively collected for 200 patients enrolled in a randomized controlled trial comparing survival with a prescribed effluent rate of 20 ml/kg/hr (standard dose) to 35 ml/kg/hr (high dose) using pre-dilution continuous venovenous hemodiafiltration (CVVHDF). Filters were changed every 72 hours. Effluent urea nitrogen (EUN) and creatinine (ECr) levels, and TEV were obtained daily. Estimated effluent dose was defined as the TEV corrected for the pre-dilution effect of the RF. Actual delivered dose was calculated as: (EUN/BUN)*TEV for urea and (ECr/SCr)*TEV for creatinine. Complete data were available for 165 patients. The difference in actual delivered dose for the standard dose compared to the high dose group was statistically significant for both measured urea and creatinine clearances (p<0.0001). For the standard dose group, there was no difference between the estimated effluent dose and actual delivered urea and creatinine clearances. For the high dose group, estimated dose based on TEV differed significantly from both the delivered urea clearance by 7.1% (p<0.0001), and the creatinine clearance by 13.9 % (p<0.0001). Direct measurement of solute clearance is indicated if providing predilutional CVVHDF.

Effluent Volume in Continuous Renal Replacement Therapy Overestimates the Delivered Dose of Dialysis

Studies examining dose of continuous renal replacement therapy (CRRT) and outcomes have yielded conflicting results. Most studies considered the prescribed dose as the effluent rate represented by ml/kg per hour and reported this volume as a surrogate of solute removal. Because filter fouling can reduce the efficacy of solute clearance, the actual delivered dose may be substantially lower than the observed effluent rate. Data were examined from 52 critically ill patients with acute kidney injury (AKI) requiring dialysis. All patients were treated with predilution continuous venovenous hemodiafiltration (CVVHDF) and regional citrate anticoagulation. Filter performance was monitored during the entire course of therapy by measuring blood urea nitrogen (BUN) and dialysis fluid urea nitrogen (FUN) at initiation and every 12 hours. Filter efficacy was assessed by calculating FUN/BUN ratios every 12 hours of filter use. Prescribed urea clearance (K, ml/min) was determined from the effluent rate. Actual delivered urea clearance was determined using dialysis-side measurements. Median daily treatment time was 1413 minutes (1260 to 1440) with a total effluent volume of 46.4 ± 17.4 L and urea mass removal of 13.0 ± 7.6 mg/min. Prescribed clearance overestimated the actual delivered clearance by 23.8%. This gap between prescribed and delivered clearance was related to the decrease in filter function assessed by the FUN/BUN ratio. Effluent volume significantly overestimates delivered dose of small solutes in CRRT. To assess adequacy of CRRT, solute clearance should be measured rather than estimated by the effluent volume.

WASHING-ELECTROKINETIC DECONTAMINATION FOR CONCRETE CONTAMINATED WITH COBALT AND CESIUM

A great volume of radioactive concrete is generated during the operation and the decommissioning of nuclear facilities. The washing-electrokinetic technology in this study, which combined an electrokinetic method and a washing method, was developed to decontaminate the concrete generated in nuclear facilities. The results of only an electrokinetic decontamination for the concrete showed that cobalt was removed to below 1% from the concrete due to its high pH. Therefore, the washingelectrokinetic technology was applied to lower the pH of the concrete. Namely, when the concrete was washed with 3 M of hydrochloric acid for 4 hours (0.17 day), the CaCO₃ in the concrete was decomposed into CO₂ and the pH of the concrete was reduced to 3.7, and the cobalt and cesium in the concrete were removed by up to 85.0% and 76.3% respectively. Next, when the washed concrete was decontaminated by the electrokinetic method with 0.01M of acetic acid in the 1L electrokinetic equipment for 14.83 days, the cobalt and the cesium in the concrete were both removed by up to 99.7% and 99.6% respectively. The removal efficiencies of the cobalt and cesium by 0.01M of acetic acid were increased more than those by 0.05M of acetic acid due to the increase of the concrete zeta potential. The total effluent volume generated from the washing-electrokinetic decontamination was 11.55L (7.2ml/g).

THE CLINICAL APPLICATION OF CRRT—CURRENT STATUS: Intensity of Continuous Renal Replacement Therapy in Acute Kidney Injury

The intensity of continuous renal replacement therapy (CRRT) is generally assessed on the basis of small solute clearance with dosing usually expressed in terms of total effluent volume per unit time (e.g., ml/kg/hour). Although several clinical trials have suggested an improvement in survival with higher doses of CRRT, results have not been consistent across all studies. The results of recent trials of intensity of CRRT are reviewed. The largest and most recent trials suggest that there is no additional benefit to using effluent flow rates in excess of 20 ml/kg/hour, although earlier studies suggested improved survival with doses of 35 to 45 ml/kg/hour.

Electro-assisted regeneration of ion exchange resins

Electro-assisted regeneration (EAR) for the mixed bed of strongly acidic cation and weakly basic anion exchange resins with the Al(OH)3 suspension in a three-compartment cell was investigated. The desalination experiments were carried out to evaluate the characteristic of the regenerated mixed resins. Experimental results showed that the efficiency of resin regeneration was strictly dependent on the voltage, regeneration time, and feed regenerant flow rate. The amount of the effluent reached 50 times the volume of the resins bed, and the conductivity was less than 1.0 μs/cm. Compared to the conventional ER, the total effluent volume of EAR was about 1000 mL more than that of ER under the same conditions, and the outlet conductivity was significantly lower. The desalination and regeneration reaction mechanisms of the mixed resins indicated the regeneration efficiency of resin with Al(OH)3 as the regenerant was much higher than that with H2O.

How effective has the Clean Water Act been at reducing pollutant mass emissions to the Southern California Bight over the past 35 years?

The Clean Water Act (CWA) has regulated discharges of contaminants since 1972. However, evaluations of the CWA's effectiveness at improving regional water quality are lacking, primarily because integration of monitoring data from multiple dischargers to assess cumulative effects is not required. A rare opportunity exists to assess CWA effectiveness by integrating mass emissions data from all major sources of contaminants to the Southern California Bight from 1971 to 2000. While the coastal population grew by 56% and total effluent volume increased 31% since 1971, mass emissions of nearly all constituents decreased since passage of the CWA, most by greater than 65%. Publicly owned treatment works were the dominant point source of many contaminants, but also accounted for the greatest reductions in pollutant discharge since 1971. As point source treatment has improved, the relative contribution of non-point sources, such as storm water runoff has increased. Despite the increased importance of storm water discharges, regional monitoring and data compilation of this source is lacking, making it difficult to accurately assess trends in non-point source discharge.

Estimating Water Flow in Drainage Pipes

Drainage pipe effluent is frequently analyzed to determine the water composition to address nutrient or contaminant transport. The total effluent volume must be known in order to determine the total nutrient or contaminant discharge. These estimates of total effluent volumes may be accomplished with flow meters; however, equipment and labor costs may be prohibitive and a qualitative method may be a practical alternative. This manuscript outlines a mathematical approach for employing Manning's formula; in which, the cross-sectional area and wetted perimeter of partially filled conduits are determined using measurements of the pipe internal diameter, the maximum depth of water in the pipe, and the coefficient of roughness. Field observations indicate that the method is a qualitative estimate of water effluent and is accurate for field approximations; however, field calibration is warranted.

A comparison of center‐based vs. home‐based daily hemodialysis for patients with end‐stage renal disease

Home hemodialysis has been a therapeutic option for almost 4 decades. The complexity of dialysis equipment has been a factor-limiting adoption of this modality. We performed a feasibility study to demonstrate the safety of center-based vs. home-based daily hemodialysis with the NxStage System One portable hemodialysis device. We also performed a retrospective analysis to determine if clinical effects previously associated with short-daily dialysis were also seen using this novel device. We conducted a prospective, 2-treatment, 2-period, open-label, crossover study of in-center hemodialysis vs. home hemodialysis in 32 patients treated at 6 U.S. centers. The 8-week In-Center Phase (6 days/week) was followed by a 2-week transition period and then followed by the 8-week Home Phase (6 days/week). We retrospectively collected data on hemodialysis treatment parameters immediately preceding the study in a subset of patients. Twenty-six out of 32 patients (81%) successfully completed the study. Successful delivery of at least 90% of prescribed fluid volume (primary endpoint) was achieved in 98.5% of treatments in-center and 97.3% at home. Total effluent volume as a percentage of prescribed volume was between 94% and 100% for all study weeks. The composite rate of intradialytic and interdialytic adverse events per 100 treatments was significantly higher for the In-Center Phase (5.30) compared with the Home Phase (2.10; p=0.007). Compared with the period immediately preceding the study, there were reductions in blood pressure, antihypertensive medications, and interdialytic weight gain. Daily home hemodialysis with a small, easy-to-use hemodialysis device is a viable dialysis option for end-stage renal disease patients capable of self/partner-administered dialysis.

Nitrogen transformation and nitrous oxide emissions from various types of farm effluents

With land disposal of the farm effluents as an accepted practice, concerns are viewed for its effect on the nitrous oxide (N2O) emissions. This study was undertaken to determine the effect land application of different farm effluents (treated farm dairy effluent (TFDE), untreated farm dairy effluent (UFDE), treated piggery farm effluent (TPFE) and treated meat effluent (TME)) have on N2O emissions from soil. N2O emissions were measured in the field using closed chamber technique. Effluents were added to the plots at a constant hydraulic loading of 25 mm with total volume of effluent applied for each plot being 50 l. Some soil properties like Soil bulk density, water filled pore space, oxygen diffusion rate (ODR), mineral nitrogen and dissolved organic carbon were measured along with the N2O flux measurement to assess their correlation with variation observed in N2O flux. The emissions rate was affected by the type of the effluent with TPFE emitting the highest (0.585 kg N2O–N ha−1 or 2.17% of the total added effluent-N) during autumn application and TME emitting the highest (0.286 kg N ha−1 0.84% of the total effluent-N added) during winter application. The difference in the N2O emissions among the effluents could be attributed to the difference in their C:N ratio. The return to pre-application N2O emissions rates within 2 weeks of autumn effluent application and 3 weeks of winter effluent application indicates that the effect of effluent application on flux is short lived. Correlation studies indicate that N2O flux was affected by some of the above mentioned soil properties.

Quality of Effluents from Channel Catfish Hatcheries in Northwestern Mississippi

AbstractSamples of water supply and effluent were collected from five commercial hatcheries for channel catfish Ictalurus punctatus in northwestern Mississippi. Hatcheries were visited three times at 2‐week intervals during the peak of the catfish spawning season. Samples were analyzed for total suspended solids, soluble and total phosphorus, total ammonia, total nitrogen, and 5‐d biochemical oxygen demand (BOD5). Net pollutant loads (effluent concentration minus inflow concentration) were low for all variables. Maximum average net loadings were 10.7 mg/L for total suspended solids, 0.13 mg/L for total phosphorus, 0.28 mg/L for total nitrogen, and 2.07 mg/L for BOD5. Because net pollutant loadings were low and groundwater supplies initially had low concentrations of solids and organic matter, effluents were of excellent quality with respect to those variables. Four of the groundwater supplies contained substantial background levels of phosphorus or nitrogen; accordingly, effluents from those hatcheries had moderate levels of those substances. The highest average effluent concentrations (ranges for all samples in parentheses) were as follows: total suspended solids, 12.3 mg/L (7‐ 19 mg/L); soluble reactive phosphorus, 0.36 mg/L (0.007–0.390 mg/L); total phosphorus, 0.45 mg/L (0.15‐ 0.53 mg/L); total ammonia nitrogen, 0.49 mg/L (0.13‐ 0.57 mg/L); total nitrogen, 0.60 mg/L (0.19–0.72 mg/ L); and BOD5, 3.03 mg/L (0.85–4.03 mg/L). These concentrations are lower than the corresponding concentrations in most potential effluent‐receiving streams in northwestern Mississippi, and total effluent volume from catfish hatcheries constitutes less than 0.02% of total annual streamflow in the region. It is therefore unlikely that catfish hatchery effluents will have a negative effect on receiving stream water quality.

A fractional dialysate collection method to estimate solute removal in continuous venovenous hemodialysis

Fractional direct dialysis quantification (fDDQ), whereby a known proportion of dialysate effluent is sampled, can reliably estimate total solute removal in intermittent hemodialysis (IHD). Our study aimed to develop and test the technique in continuous venovenous hemodialysis (CVVHD). Twenty dialysate collections (mean duration 23.5 hours, range 17.25 to 26.6) were performed in 12 patients on CVVHD. An infusion pump diverted 10% of the total effluent volume to the fractional collection (fc), the remainder being channeled into the bulk collection (bc). Both fc and bc were collected on ice and assayed for urea nitrogen (UN) and creatinine (Cr). Actual solute removal (ASR) was calculated from the measured effluent volume and solute concentrations of the fc and bc. Estimated solute removal (ESR) was calculated from the product of the fc solute concentration and effluent volume. All fc/bc samples in 15 out of 20 collections underwent gram stain and aerobic/anaerobic culture. Bland-Altman analyses suggested good agreement between ASR and ESR [absolute values of percentage differences: 95% CI = 1.73, 5.17% (UN); 1.88, 4.31% (Cr)]. Favorable concordance correlation coefficients confirmed this [rc = 0.995 (UN), 0.997 (Cr)] and were apparently unaffected by heavy pseudomonal growths in 4 out of 7 culture positive collections [rc = 0.997 (UN), 0.997 (Cr); culture negative (N = 8), rc = 0.996 (UN), 0.997 Cr)]. fDDQ, using 24-hour, pump-assisted, cooled fractional dialysate sampling reliably estimates total solute removal and provides a practical alternative to total dialysate collection in assessing delivered dialysis dose.

ALTERNATIVE INDICES OF THE OVERLOAD FREQUENCY IN AN EFFLUENT RE‐USE SYSTEM

An effluent re-use system is examined in which all effluent was stored until it could be used for the irrigation of crops, the storage having sufficient capacity to limit overloading to one in ten years. Three methods for estimating the required storage capacity were compared using climate data from four locations in New South Wales, Australia. A daily soil water budget identified the irrigation opportunities, and a storage subroutine in the budget calculated the peak storage requirement in each year The first method used the ninth decile in the cumulative probability distribution of the annual peak storage requirements as a direct estimate of the storage capacity with a 10% frequency of overloading. The other methods used the peak storage requirement in selected design years. These represented years with either the tenth smallest annual irrigation potential or the tenth largest annual rainfall. Methods which used design years tended to underestimate the storage requirements because the indices did not assess the daily distribution of rainfall within a month or year. Although the overload frequency was set at 10%, the overload was less than 2% of the total volume of effluent because overloading did not occur throughout the year.